Let’s jump straight to the answer: Botanists DO NOT recognise large-form monstera and small-form monstera (sometimes called borsigiana) as different species or a subspecies. Both are the same plant, simply expressing different growth forms possible within the natural diversity of the monstera deliciosa species.
So why do some many collectors consider them to be different plants? It goes way back to when these plants first started being distributed around the world.
Early collectors took specimens from the the forests of South America and planted them in botanical gardens, greenhouses, backyards, and into the hands of private collectors in many different regions.
Each isolated population had minimal genetic diversity and varying growing conditions, so eventually several distinct forms took shape.
The small and large forms have been massively propagated and are now the the two standard versions found in stores and collections in Europe/America/Australia. Neither truly resembles the “common” form found in the wild, which is—as you might expect—somewhere in between small and large.
There’s another lesser-known form that’s smaller than small-form, but has the larger fenestrations and more compact growth habit of the large-form. This form is, rather appropriately, called “monstera compacta” and seems to have emerged in Asia.
What form is my monstera deliciosa?
If your monstera doesn’t have little circles and grows like a vine, it’s probably small form. If the leaves are bigger and more fenestrated, but the plant grows fairly compactly, it’s probably a large form.
What about variegated monsteras?
Monstera Thai Constellation was created from large-form monsteras. Supposedly growers in Asia have produced a Thai Constellation based on the “compacta” form, but these don’t seem to have made it to the west just yet.
Monstera “albo” is almost always small form deliciosa. Large form albo does apparently exist, but it’s exceeding rare compared to the standard small form version.